According to Bambu Studio release note1-10-0, feature 6:
Edit filament information during printing: P-series and A-series printers now support editing filament information during printing, even for filaments not currently in use or in ‘Auto-Fill’ mode. This includes both external spool slots and AMS slots. Users can replace an empty spool before it’s fully consumed, and the new spool will automatically continue the current print.(Supported P-series firmware version:01.07.00.00,supported A-series firmware version:01.04.00.00)
And the P1 firmware version 01.07.00.00 says: Only the filament that is not in use can be edited.
This would be perfect if the same firmware update was available for the P2S. I assumed when it said P-series, the P2S was included. The P2S is at 01.01.01.00 and does not seem to allow for unloading and loading filament during a print or print pause.
I had a 5-color print I downloaded that included a pause for the swap of colors in one of the AMS slots. The option to unload/load the old to new color was not present. So, I manually pulled out the old color (not being used at that moment) and loaded the new color. However, the filament never loaded and the AMS slot showed a question mark in both Bambu Studio and on the P2S screen. There was no way to edit the slot either. I tried to sync the filaments but nothing worked. It ended up printing with a different color recognized as being in the AMS instead.
So, I tried the print again (the first time I didn’t know I wouldn’t have the unload/load option and thought I’d just done it wrong). At the pause, I ended up manually doing it again but really pushed the filament into the tube and the slot lit up. I again tried syncing/remapping until I crashed Bambu Studio and it wouldn’t let me do anymore, including resuming. The one thing I did slightly differently was to say the filament was generic instead of the Bambu brand it was when re-syncing. So I resumed from the P2S screen and it did use the 5th color even though it still showed no filament information on screen. It did work, but don’t really know how.
I ran into it again when I tried a white and black print meant for no AMS. It had a pause to swap colors but I couldn’t because the white was loaded and in the tube, unlike the above example. The AMS kept trying to feed it in against my attempt to pull it out. I ended up cancelling the print hoping to print only the last black layer by itself. I could not figure out how.
Does anyone have any suggestions or know anything about a firmware update like the P1 has? I am fairly new to this but am already finding this annoying since it should be straightforward. I even tried to figure out how to convert a existing print from no AMS to using AMS for that 2nd one, but couldn’t quite find exact instructions or my equipment didn’t have the options listed.
There are a few firmware and software release notes that mention ‘P-series’ support but I’m not so sure currently apply to the P2S. Like you, I also assumed P-series features include the P2S. I’ve noticed the notes for v1.10.0 (2024) use the term ‘P-series’ but the recent v.2.5.0 (2026) makes a distinction between support for the P1S and P2S.
For example, the v.2.5.0 notes mention aborting loading/unloading filament, but despite the P2S releasing last year, it is not currently a supported printer:
I could be wrong, recent experience tells me that (at least when it comes to release notes) Bambu’s terminology shifted with the P2S and its teething issues since release. “It should be straightforward” has been on a constant loop of late (currently having a fit over filament swap g-code causing auto-purges, even if purging volumes are set to ‘0’. Not an issue on other models. Zero means zero, why is my P2S still pooping! 
)
I did try replicating your issue but Load/Unload in Bambu Studio remains greyed out for the entire print and my AMS would not accept a newly placed spool mid-print. No such option appears in my P2S’ display. Unfortunately, I don’t have a 5+ colour print handy to try it with so hopefully another user can step in. At this stage, I’d be taking any P-series ‘features’ with a grain of salt 
This is terrible 
I’m printing mostly in PETG. I have one spool in the AMS and a second in the dryer. I can’t put the second spool in the AMS while printing.
This would be super-useful when you’re at the end of the first spool, so that when it runs out, AMS could switch to the second spool.